SSH is a fairly extensive topic and I will only cover the basics of establishing a connection and transferring files here.
If you’re already on a UNIX/linux server, chances are SSH is already installed. You can check this by typing which ssh. To securely connect to another box, SSH is ideal because it provides an encrypted connection so your password cannot be snooped by any dubious ‘interlocutors’.
At the command prompt simply enter ssh -l username targetHost. The -l switch indicates it’s a login, specify your username and the target host and that’s it. If the remote host is not running SSH or you do not have logon rights of course this will not work.